The Curiosity rover on Mars has found more signs that the planet’s surface was one a wet environment, in a new report. It has been drilling into rocks at a site named Garden City which forms part of Mount Sharp which has always been the primary target of this mission.

The minerals at three different levels were analysed, revealing three different compositions. The first section, which was named Confidence Hills, had a high proportion of clay minerals and hematite, both of which form under wet conditions.

The second comprised jarosite, an oxidized mineral containing iron and sulfur that forms in acidic conditions and the third contained virtually no clay minerals, which may have been removed by other ingredients to leave the predominantly silicate mineral behind.

The exposed mineral two-tone veins at the same site are evidence of fluid movement through fractures in the rocks. "Some of them look like ice-cream sandwiches: dark on both edges and white in the middle," said Linda Kah, a Curiosity science-team member at the University of Tennessee, Knoxville. "These materials tell us about secondary fluids that were transported through the region after the host rock formed."

This news comes at the same time as researchers in Denmark released an estimate of the amount of water bound up in glaciers that exist on the surface of Mars, covered by dust which prevents them from sublimating and disappearing. Using radar data gathered from the Mars Reconnaissance Orbiter, the team estimated that there is sufficient ice trapped in these glaciers to cover the whole Martian surface to a depth of 1.1m as they described in Geophysical Research Letters.

The calculations on the glaciers, which exist in the northern and southern hemispheres of Mars, will help to work out what happened to the planet’s water.